1. Field of the Invention
The invention relates to a deflection yoke for a cathode ray tube (CRT), more particularly, a color CRT.
2. Background of the Related Art
An in-line type electron gun generally used in a color CRT has red xe2x80x98Rxe2x80x99, green xe2x80x98Gxe2x80x99, and blue xe2x80x98Bxe2x80x99 color electron beams arranged horizontally in a line. A self-converging type deflection yoke is required in the CRT to converge the three electron beams onto one point on a fluorescent surface using a non-uniform magnetic field.
FIG. 1 of the present application shows a related art color CRT. The color CRT of FIG. 1 is provided with a panel 1 at a front of the CRT. A fluorescent surface 3 formed of red R, green G, and blue B fluorescent materials is coated on an inside surface of the panel 1. A shadow mask 2 is positioned adjacent the fluorescent surface 3 and selects a color of the electron beams incident on the fluorescent surface. A funnel 6 is attached to the back of the panel 1 and provides an inner space under vacuum. An electron gun 5 is fitted inside a tubular neck part of the funnel and emits the electron beams. A deflection yoke 4 is provided around an outer circumference of the funnel 6. The deflection yoke 4 deflects the electron beams in the horizontal or vertical direction.
Referring to FIG. 2, the deflection yoke 4 is provided with one pair of horizontal deflection coils 41 that deflect the electron beams emitted from the electron gun 5 inside of the CRT in a horizontal direction, one pair of vertical deflection coils 42 that deflect the electron beams in a vertical direction, and a ferrite core 44 that reduces a loss of magnetic force caused by currents in the horizontal and vertical deflection coils. A holder 43 fixes the physical relative positions, fastens, and couples the horizontal deflection coils, the vertical deflection coils, and the ferrite core, provides insulation between the horizontal deflection coils and the vertical deflection coils, and facilitates coupling of the yoke 4 to the CRT. A COMA free coil 45 fitted to a neck side of the holder improves a COMA aberration caused by a vertical barrel type magnetic field. A ring band 46 fitted to the neck side of the holder mechanically couples the CRT with the deflection yoke. Magnets 47 fitted to an open end of the deflection yoke correct a raster distortion (hereafter called distortion) on the picture.
The horizontal deflection coils of the deflection yoke 4 include upper and lower deflection coils connected in parallel, as shown in FIG. 3B. A horizontal deflection current, as shown in FIG. 3A, is applied to the upper and lower deflection coils to form a horizontal deflection magnetic field, which deflects the electron beams from the electron gun 5 in the horizontal direction.
The deflection yoke 4 may be categorized depending on the shapes of the horizontal and vertical deflection coils 41 and 42, and the ferrite core 44, as set forth in table 1 below. That is, as shown in FIGS. 4 and 5, if the horizontal and vertical deflection coils are circular, the ferrite core is circular. As shown in FIG. 6, if the horizontal and the vertical deflection coils 41 and 42 are rectangular, the ferrite core is rectangular.
Since the RAC type CRT deflection yoke 4 has a rectangular deflection coil and ferrite core, in the RAC type CRT deflection yoke 4 there is a shorter distance to the electron beams compared to the circular deflection yoke 4, which provides better deflection sensitivity.
In general, the related art deflection yoke 4 has a current having a frequency equal to, or higher than, 15.75 KHz flowing through the horizontal deflection coil 41. This current deflects the electron beams in the horizontal direction using a magnetic field formed as the current flows through the horizontal deflection coil 41. The related art deflection yoke 4 generally has a current having a frequency equal to 60 KHz flowing through the vertical deflection coil 42. This current deflects the electron beams in a vertical direction using a magnetic field formed as the current flows through the vertical deflection coil 42.
In most cases, a self-convergence type deflection yoke 4 is used, in which the three electron beams are converged on the screen using a nonuniform magnetic field formed by the horizontal and vertical deflection coils without providing additional circuitry and device(s). That is, distributions of the windings of the horizontal deflection coil and the vertical deflection coil are adjusted to form a barrel or pin-cushion type magnetic field at respective parts (the opening part, the middle part, and the neck part) of the CRT so that the three electron beams undergo different deflection forces according to the positions of the three electron beams to converge the electron beams from different starting points to the same arrival point on the screen 1.
If the magnetic field formed by the current through the deflection coil is not adequate for deflecting the electron beams to all parts of the screen, the ferrite core 44, which has high permeability, is employed to minimize the loss of the magnetic field on the returning path, and to enhance a magnetic field efficiency and force.
Referring to FIG. 7, each of the one pair of horizontal deflection coils 41 has a rectangular upper horizontal deflection coil and a lower horizontal deflection coil, connected in parallel as shown in FIG. 3B, in which horizontal deflection currents in a saw tooth form are formed, forming a pin-cushion type horizontal deflection magnetic field.
There are two kinds of deflection yokes. As shown in FIGS. 4 and 5, since a circular deflection yoke 4, with circular horizontal and vertical deflection coils 41 and 42 and a circular ferrite core 44, has a ratio of inside surface areas of the neck part to the opening part of at least greater than 10 times, a deflection center of the deflection coil is deviated toward the neck part. Thus, it is necessary to arrange the deflection yoke inclined toward the screen in order to avoid a BSN (Beam Strike Neck) characteristic, a phenomenon in which the electron beams from the electron gun land on an inside surface of the funnel, which results in poor deflection sensitivity.
As shown in FIGS. 6 and 7, the RAC type deflection yoke 4, with rectangular horizontal and vertical deflection coils 41 and 42, and a rectangular ferrite core 44, deflects electron beams in the horizontal direction by a force inversely proportional to a third power of a distance between an inside surface of the horizontal deflection coil and the electron beams, according to Flemming""s left hand rule, as the three electron beams (i.e., red, green, and blue) from the electron gun 5 pass through the horizontal deflection magnetic field. Accordingly, the rectangular horizontal and vertical deflection coils have horizontal and vertical deflection sensitivities enhanced by approx. 20-30% as the distances between the electron beams and the deflection coils are shorter by a range of 20% compared to the related art circular deflection yokes.
However, the related art CRT deflection yoke 4 has the following problems. First, the circular deflection yoke with the circular deflection coils is unfavorable because of its poor deflection sensitivity due to the unnecessary distance between the electron beams and the deflection coil, and is particularly unfavorable in the case of a wide angle deflection yoke. The wide angle deflection yoke is not applicable to a high definition and high frequency deflection yoke.
Second, the ferrite core 44 used in the RAC type deflection yoke has a shrinkage rate of up to 20%, requiring a fabrication tolerance to be xc2x12% due to limitations in the fabrication process. Further, the related art ferrite core 44 having a rectangular inside surface for enhancing the sensitivity of the deflection yoke has different inside diameters at left and right sides, the top, and the bottom. As the rectangular ferrite core requires the fabrication tolerance during the fabrication process to be greater than three times that of the existing circular core, and has a rectangular, not circular, inside surface that is difficult to polish for accurate dimensional control, the rectangular ferrite core has the problem that a production yield is around 50% in comparison to the existing circular inside surface core, at around 200% of the cost.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.
An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
Accordingly, the invention is directed to a deflection yoke in a CRT that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Another object of the invention is to provide a deflection yoke in a CRT which permits, not only an improvement in deflection sensitivity and a reduction in inside surface dimensions of the ferrite core, but also provides for easy polishing of the inside surface, thereby significantly improving production yield, and the ferrite core dimensions.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve at least the above objects in whole or in part and in accordance with the purpose of the invention, as embodied and broadly described, a cathode ray tube according to the invention includes a panel having a fluorescent surface comprised of red R, green G, and blue B fluorescent materials, a funnel fitted to a rear of the panel that provides an inner space under vacuum, an electron gun fitted inside of a tubular neck part at a rear of the funnel that emits electron beams, and a deflection yoke that deflects the electron beams in a horizontal or vertical direction, the deflection yoke including horizontal and vertical deflection coils that deflect the electron beams emitted from the electron gun in a horizontal or vertical direction, a ferrite core that reduces a loss of magnetic force caused by the horizontal and vertical deflection coils thereby enhancing magnetic efficiency, and a holder that holds the horizontal deflection coil, the vertical deflection coil, and the ferrite core at required positions, provides insulation between the horizontal and vertical deflection coils, wherein the screen end, or side of the horizontal and/or vertical deflection coil has a substantially rectangular shape and the ferrite core is circular or elliptical.
The horizontal and/or vertical deflection coil may have a circular or elliptical shape on the neck end, or side.
Further, the ferrite core may have a circular or elliptical shape on the screen and neck ends, or sides.
Further, there may a least and a greatest distance between the ferrite core and an opposite deflection coil with reference to a plane perpendicular to a tube axis. The difference between the greatest distance and the least distance may be greatest on a screen side end, or edge.
Furthermore, a difference between the greatest and least distance may become gradually greater starting from a neck end, or side to a screen end, or side.
The least distance is preferably in a range of approximately 0-1.0 mm, and the greatest distance is preferably in a range of approximately 1-30 mm.
To further achieve at least the above objects in whole or in part and in accordance with the purposes of the invention, as embodied and broadly described, a cathode ray tube is provided including a panel having a fluorescent surface, a funnel fitted to rear of the panel and configured to maintain an inner space formed between the panel and funnel in vacuum, an electron gun fitted inside of a neck part of the funnel for emitting electron beams, and a deflection yoke configured to deflect electron beams in a horizontal and/or vertical direction. The deflection yoke includes horizontal and vertical deflection coils configured to deflect the electron beams emitted from the electron gun in a horizontal and/or vertical direction, and a ferrite core configured to reduce a loss of magnetic force caused by the horizontal and vertical deflection coils, thereby enhancing a magnetic efficiency of the cathode ray tube, wherein a screen side of at least one of the horizontal and vertical deflection coils has a substantially rectangular shape, and the ferrite core is circular or elliptical.
Additionally, to achieve at least the above objects in whole or in part and in accordance with the purposes of the invention, as embodied and broadly described, a cathode ray tube is provided including a panel having a fluorescent surface, a funnel fitted to rear of the panel and configured to maintain an inner space formed between the panel and funnel in vacuum, an electron gun fitted inside of a neck part of the funnel for emitting electron beams, and a deflection yoke configured to deflect electron beams in a horizontal and/or vertical direction. The deflection yoke includes horizontal and vertical deflection coils configured to deflect the electron beams emitted from the electron gun in a horizontal and/or vertical direction, and a ferrite core configured to reduce a loss of magnetic force caused by the horizontal and vertical deflection coils, thereby enhancing a magnetic efficiency of the cathode ray tube, wherein there is a least and a greatest distance between the ferrite core and at least one of the horizontal and vertical deflection coils opposite to the ferrite core with reference to a plane perpendicular to a tube axis.
Additionally, to achieve at least the above objects in whole or in part and in accordance with the purposes of the invention, as embodied and broadly described, a deflection yoke is provided including horizontal and vertical deflection coils configured to deflect the electron beams emitted from the electron gun in a horizontal and/or vertical direction, and a ferrite core, wherein a screen side of at least one of the horizontal and vertical deflection coils has a substantially different shape than the ferrite core.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.